Modem pass through for remote testing

ABSTRACT

A lab network access server is disclosed in accordance with an embodiment of the present invention. The lab network access server is coupled to a customer network server through a packet switching network. The customer modem device includes a customer modem device and is coupled to an end-user modem device employed by an end-user. In a diagnostic scenario, the end-user initiates a call through the customer network access server modem device, which is setup for pass through operations. The customer network access server, upon receiving the call information, routes the call information to the lab network access server for termination thereof. The lab network access server operates to diagnose problems associated with the customer modem device and includes a lab modem device. Upon the customer modem device failing to successfully communicate with the end-user modem device, the lab modem device receives a succeeding call from the end-user modem device using a pass-through mode of tunneling, through the packet switch network, and terminates the succeeding call thereby allowing diagnosis and debugging of the failure associated with the customer modem device to be performed at the location of the lab network access server. In a modem wholesale scenario, the same setup is used as a service to terminate modem calls in a remote location when a customer only has voice-over-IP capabilities.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to detecting problems arisingfrom the use of a modem device that is positioned in a remote location(field modem debugging) and particularly to increasing the speed of suchmodem debugging. Additionally, the present invention can be used tosupport a service for offering remote wholesale modems through avoice-over-Internet Protocol (VoIP) carrier from the end-user to thewholesale modem banks.

2. Description of the Prior Art

In modern communication systems, information is transmitted from a pointof origin to a destination point often through packet networks such asan Internet Protocol (IP), frame relay or Asynchronous Transfer Mode(ATM) networks. The point of origin and the destination point each maybe any number of devices such as a Plain Old Telephone System (POTS), afax machine, modem attached to a personal computer (PC) and the like.The information emanating from any one of such devices may be initiatedin one country and received at another.

As an example, when a phone call is initiated from a telephone unit inGermany, in order for it to be transmitted over an IP network, whichwould either be the Internet or any other propriety IP network, it isforwarded to a local public switching telephone network (PSTN) inGermany. The telephone call is forwarded from the PSTN to a localnetwork access server (NAS) in the form of compressed digital signals.Inside of the NAS, a Digital Signal Processor (DSP) device receives thevoice calls from the PSTN in the form of digitized voice signals orpulse code modulation (PCM) samples, as defined by an industry standard,the ITU-T G.711.

Inside of the NAS, the voice signals are packetized (voice samples) intoReal-time Transport Protocol (RTP) packets and sent over the IP network.RTP provides end-to-end network transport functions for applicationsthat transmit real-time data, such as audio and video. The informationin the form of RTP packets is transmitted from the IP network to a localNAS in the U.S. wherein the packets are reassembled into voice signals.The DSP inside of the NAS in the U.S. then transmits the voice signalsto a local PSTN. Finally, the latter forwards the voice calls to thedestination phone unit in the U.S.

To the end users at the point of origin and the destination point, theabove mode of transmitting phone calls, also known as the IP phone orVoIP, is indistinguishable from a regular phone call, which istransmitted over the PSTN network. The call is tunneled through the IPnetwork in order to connect the two PSTNs. Accordingly, using the IPphone to establish connection between 2 communication devices isalternatively called tunneling.

There are two distinct ways in which tunneling can be accomplishedbetween two people, one who is located in Germany and the other who islocated in the U.S., when the originating and destination (orterminating) devices are modem devices. The first mode is referred to as“pass-through”. In the pass-through mode of tunneling, the NAS inGermany recognizes an incoming modem signal from the local PSTN bydetecting a modem tone. The NAS subsequently sends a message to the IPnetwork alerting the latter that high priority information is about tobe transmitted so that the IP network can provide quality of service.The voice signals are bundled together as RTP packets in the NAS andtransmitted over the IP network to a local NAS in the U.S. The receivingNAS reassembles the RTP packets as voice signals and sends them over toa local PSTN, which in turn forwards them to their destination modemdevice.

In pass-through, the transmitting NAS sends the voice calls in the formof PCM samples in both directions simultaneously. In other words, theNAS establishes a full-duplex communication channel. The data rate of aPCM voice call is 64 kbits/sec when data is sent in one direction(half-duplex) and 128 kbits/sec when voice signals are sent in bothdirections at all times. In the latter case, data is constantly beingtransmitted over the IP network for every single application. This is aconsiderable amount of bandwidth for one application alone, which makespass-through an expensive method of tunneling.

Alternatively, tunneling can be accomplished using a method known asdemodulation/remodulation, or relay. In relay, the NAS in Germanyconverts the PCM bytes into a word representing the linear digitalequivalent of the analog signal received by the modem. Thereafter, theconverted digital signal is demodulated into data bits. The demodulatedbits are then forwarded across the IP network to the destination NAS inthe U.S. The latter remodulates the bits into voice samples, which arethen transmitted to the destination point by sending them through thelocal PSTN. In relay, data is transmitted when the latter is availablewith a lower rate transmission than in pass-through because in relayonly modem data is transmitted without the sampled modulated signals. Inaddition relay transmits data in the direction that data is available.The transmission of data is half or full duplex depending on whether thedata is transmitted in one or both directions. In pass-through, however,modem signal data is transmitted in both directions at all times and ata maximum rate of 64 kbps regardless of whether there is any modem datato be transmitted or not because the modem signals must be continuouslytransmitted to keep the modems at both ends operational and synchronous.

The pass-through mode of tunneling is more time-sensitive to delays thanrelay since in the former case, raw data rather than demodulated bits isbeing transmitted. Additionally, in pass-through, the likelihood of databeing adversely affected by packet loss, packet corruption and packetdelay jitter is less than it is in relay mode. As an example, in IPphone, using pass-through transmission, the connection has to be suchthat voice samples are not delayed or lost during transmission.Accordingly, the demand for bandwidth during voice transmission is high.On the other hand, faxes are transmitted using relay in the form ofmodulated bits where it is more tolerable to wait for modulated bits toarrive as a fax page, which makes relay less sensitive to networksimpairments such as time delays and packet loss than the pass-throughmode of tunneling. This is the method of voice data transport.

There are several reasons for the failure of a modem to establishcommunication. The most common ones are related to firmware problems.Most common problems with modems, such as the modem 38, have been knownto relate to the modem's software (or firmware) and, in particular, tothe incompatibility of the software with the modem hardware in which thesoftware is being employed. For instance, the version of the software inthe server modem may be incompatible with the specific client modem inwhich it is used or it may be that the software is incompatible with ornot robust enough for the environment in which the modem is located.

At the present time, problems with the server modem, at the point oforigination, (commonly referred to as the customer's server modem) areinvestigated by dispatching diagnostic equipment to the site of thecustomer's NAS. The diagnostic equipment must be inserted in the datapath within the customer's NAS in order to analyze the server modem'sbehavior and to particularly monitor negotiations between the user'sclient modem and the server modem located within the NAS at thedestination point. The analyzing device samples data on the transmissionlines which couple the PSTN on the originating side of the communicationpath with the customer's NAS. Generally such transmission lines are ofeither T1 or E1 type.

Twenty-four channels of voice or modem channels are included in a T1transmission line and 30 channels of voice or modem channels areincluded in an E1 transmission line.

However, there are limitations associated with dispatching equipment tothe field. For example, if there are a large number of customers who areexperiencing difficulties with their server modem connections at any onetime there may not be a sufficient number of analyzing devicesavailable. Moreover, the customer's NAS may be located in a physicallyremote location with respect to the diagnostic equipment and thus not beeasily accessible to the engineers and/or technicians.

In light of the above, it is desirable to route and terminate the callin a location that maintains a rich debugging and instrumentationenvironment with appropriate probes and with the necessary capability tomonitor the problem in real time.

SUMMARY OF THE INVENTION

Briefly, an embodiment of the present invention includes a lab networkaccess server coupled to an end-user client modem device via a customerserver modem device and through a packet switching network. The labnetwork access server is coupled to a customer access network serverthrough the packet switching network using a VoIP connection. Thecustomer access network server includes the customer server modemdevice. The customer server modem device is coupled to the end-userclient modem device over a Public Switching Telephone Network (PSTN).The lab network access server operates to diagnose problems associatedwith the customer server modem device and includes a lab server modemdevice. The end-user client modem device attempts to establish a callwith the customer server modem device but instead of terminating thecall at the customer server modem device, the customer network accessserver forwards or tunnels the call to the lab server modem device usinga tunneling method thereby terminating the call that was initiated bythe end-user modem device at the lab network access server.

The foregoing and other objects, features and advantages of the presentinvention will be apparent from the following detailed description ofthe preferred embodiments which make reference to several figures of thedrawing.

IN THE DRAWINGS

FIG. 1 shows a network communications system 10 employing modemtermination through pass-through mode of tunneling in accordance with anembodiment of the present invention.

FIG. 2 shows a network topology for a communications system 50 inaccordance with an embodiment of the present invention.

FIG. 3 shows a signal flow chart in a network access server device.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

The present invention employs voice-tunneling infrastructure fordiagnosing problems associated with a modem in termination applications.Utilizations other than diagnosing problems may be had with the presentinvention in that modem termination may be used for applications otherthan diagnosis to save costs that would otherwise be incurred. Forapplications such as browsing the Internet, a modem call is terminatedat the NAS and converted into IP packets.

Referring now to FIG. 1, an embodiment of the present invention is shownto include a network communications system 10 between a point of originand a destination point, each of which may be any number of devices suchas telephone units, personal computers, modems, fax machines, etc. InFIG. 1, the communications system 10 is shown to include a point oforigin 46 and a destination point 12, which are shown to be two personalcomputers (PCs). The communications system 10 is also shown to includethe two PSTNs 16 and 42 and three network access servers (NASs) 20, 28and 36 as well as the packet network 24, which may be IP, frame relay orATM network. In the embodiment of the present invention, as shown inFIG. 1, the network 24 is shown to be an IP network, which may be theInternet or any other type of IP network known to those skilled in thefield. Each of the NAS devices is shown to include a modem such thatmodems 32, 30 and 38 are located inside of the network access servers20, 28 and 36, respectively.

According to one embodiment of the present invention, as exemplified bythe communications system 10, PC 46 communicates either with the PC 12or with the NAS 28. In order to establish either of these connections,PC 46 is coupled to the PSTN 42 through a transmission line 44. The PSTN42 is coupled to the NAS 36 through the transmission line 40, which inone embodiment of the present invention is a high speed transmissionline such as a T1/E1 line or any telephone company (Telco) TDM transportline such as optical-OCx, T3/E3 and the like. Network access server 36is coupled to the IP network 24 through the transmission line 34, whichin one embodiment of the present invention is an Ethernet connection.

The network access servers (NAS) 20 and 28 are in communication with theIP network 24 through the communication lines 22 and 26, respectively.Network access server 20 is in communication with the PSTN 16 via thetransmission line 18 and the PSTN 16 is in communication with the PC 12through the transmission line 14.

When the two personal computers, 46 and 12, are communicating with eachother, the IP network 24 provides a bridge between them. Such a mode ofcommunication between the two PCs is commonly referred to as tunnelingwherein the connection between the two end points is established bypassing the information through the IP network 24 rather thanterminating the call at a point in the IP network 24 (an example of whenthe call in the IP network is terminated is when a search is performedon the Internet). The presence of the IP network 24 and the two networkaccess servers 20 and 36 is indistinguishable to the PCs 46 and 12 fromthe case where the two PSTNs 42 and 16 are directly communicating witheach other.

While not shown in FIG. 1, each of the PCs 46 and 12 is equipped with amodem for transmission and reception of the information. Alternatively,the two personal computers 46 and 12 may be replaced with two telephoneunits for transmission of information in the form of voice calls inanalog format.

According to another embodiment of the present invention, the PC 46communicates with the NAS 28. In such a case, the informationoriginating at the PC 46 is transmitted to the NAS 28 by tunnelingthrough the IP network 24. Once the information in the form of voicesignals arrives at the NAS 28, it is terminated at the modem 30 insidethe NAS 28 rather than at a PC or a telephone unit.

Referring still to FIG. 1, information in the form of voice signals istransmitted from the PSTN 42 to the NAS 36 and is then forwarded to aTelco network, such as the PSTN 16 through the IP network 24. In thismanner, the IP network 24 provides a bridge between the two PSTNs 42 and16. The voice information is then transmitted from the PSTN 16 to itsdestination point, which in FIG. 1 is shown to be the PC 12.

However, when the information is forwarded through the IP network 24 tothe modem 30, the voice call is no longer terminated at a PC or a phoneunit. Rather, it is terminated inside the modem 30. Accordingly, themode of transmission from the PC 46 to the NAS 28 is referred to asmodem termination.

It should be noted that information is forwarded through the IP network24 to the modem by specifying the modem's IP address.

There are two ways of tunneling when 2 modems are communicating witheach other as in FIG. 1. In the first mode, known as pass-through, theNAS 36 identifies the incoming voice signals as modem signals being thatthese signals originated in a modem (not shown) residing inside of thePC 46. The NAS 36 then sends a message to devices included within the IPnetwork 24 alerting the latter of high priority information that isabout to be transmitted. This provides an opportunity for devices withinthe IP network 24 to provide quality of service for transmission of thehigh priority information.

Once the voice information reaching the NAS 36 is detected as modemcalls, two additional functions are performed inside of the NAS 36.First, a group of signals arriving at the same time are bundled togetherand turned into RTP packets and transmitted over the IP network 24either to the NAS 20 or to the NAS 28 as dictated by the destinationaddress of the voice signals. If the RTP packets arrive at NAS 20, thelatter reassembles the RTP packets into voice signals and transmits themto the PSTN 16 and the PSTN 16 forwards the same onto the destinationpoint PC 12. However, if the destination of the RTP packets is NAS 28,upon arrival, NAS 28 reassembles the RTP packets into voice samples andrather than sending them to another PSTN, it turns them over to themodem 30. Thus, the call is terminated using the pass-through mode oftunneling according to one embodiment of the present invention asdepicted in FIG. 1.

The second method of tunneling is referred to as modulation/demodulationor relay wherein modem 38, upon receiving voice signals, demodulates thesame into bits (or partially terminates the voice signals). The networkaccess server 36 subsequently forwards the demodulated bits over the IPnetwork 24 either to the NAS 20 where they are remodulated into voicesignals by the modem 32 or to the NAS 28 where they are remodulated intovoice signals by the modem 30.

One of the advantages of the relay mode of tunneling versus thepass-through mode of tunneling is that the former transmits data whendata is available and at a lower rate since in relay only modem data istransmitted without the sampled modulated signals. In addition, relaytransmits data in the direction that data is available. The transmissionof data is half or full duplex depending on whether the data istransmitted in one or both direction. In pass-through, however, modemsignal data is transmitted in both directions at all times and at amaximum rate of 64 kbps regardless of whether there is any modem data tobe transmitted or not because the modem signals must be continuouslytransmitted to keep the modems at both ends operational and synchronous.

Communication between the end points 46 and 12 is disrupted when eitherof the NAS 36 or 20 fails to establish a connection. Experience hasshown that if the problem lies within the originating NAS 36, it islikely due to the modem 38 failing to establish a connection. Mostcommon problems with modems, such as the modem 38, have been known torelate to the modem's software (or firmware) and, in particular, to theincompatibility of the software with the modem hardware in which thesoftware is being employed. Additionally, the modem software may beincompatible with the environment in which the modem is located.

When a modem at the point of origination, i.e. the customer's modem, issuspected of malfunctioning, the prior art method of investigation is todispatch diagnostic equipment to the physical site of the modem, whichis generally located inside of the customer's NAS. In FIG. 1, thecustomer's modem 38 is shown to be located inside of the NAS 36. Thediagnostic equipment is a PCM signal capture and analysis devicedesigned to monitor negotiations between the customer's modem 38 and thedestination modem 32. The diagnostic device monitors voice samples sentover the transmission line 40. However, there are obvious limitationsassociated with dispatching equipment to the field. For instance, thecustomer's NAS may be located in a physically remote region, which maynot be easily accessible. Moreover, in the case where there are a largenumber of customers experiencing problems with their modem connection atany give time, there may not be an adequate number of diagnostic devicesavailable.

According to one embodiment of the present invention, as shown in FIG.1, when connection between the PC 46 and the customer's modem 38 cannotbe established, rather than terminating the incoming call at thecustomer's modem 38, the call is routed through the IP network 24 andterminated at modem 30 located in the NAS 28. If the NAS 28 is locatedin a diagnostic laboratory, where facilities accommodate for a richdebugging and instrumentation environment, potential problems can bemonitored in real-time and relevant diagnostic tests can be readilyperformed to detect and to potentially resolve the problem. In addition,the need to dispatch an engineer and/or a technician with a diagnosticdevice to the customer's NAS 36 is eliminated or reduced. Furthermore,installing the diagnostic equipment in the customer's NAS causes aninterruption in service for the customer whereas using the method of thepresent invention avoids any disruption to the customer of the normaloperation of the network. In the case of the present invention, the callthat originated at the PC 46 can be routed through the IP network 24 andis terminated at modem 30.

While not shown in FIG. 1, the NAS 28 alternatively includes two modemdevices, a first modem device for performing processing of signalsreceived from the IP network 24 to conform the same to voice signals anda second modem device, coupled to the first modem device, for receivingTDM voice signals and operating as a termination point.

Additionally, the network communications system 10 may be employed formodem “wholesaling”. That is, rather than performing diagnostics ordebugging functions, the NAS 28 may serve to terminate modem calls in alocation that is remote to the NAS 36 for a customer who has onlyvoice-over-IP capabilities. In this manner, a secondary use of thepresent invention is to provide remote modem wholesale service when thecustomer NAS only supports VoIP and the end-user is trying to connectwith a modem.

FIG. 2 shows a network topology for a communications system 50 forillustrating the details of modem termination in accordance with anembodiment of the present invention. In communications system 50, an enduser working at the PC terminal 52 transmits information through themodem 56 in the form of telephone calls. The arrow 54 indicates theconnection between the PC 52 and the modem 56. The phone call isterminated in a modem (not shown) within the NAS 70, which is positionedlocally with respect to the party monitoring or diagnosing problems,such as in a diagnostic lab.

The communications system 50 includes a user's PC 52, a user's modem 56,a public Telco network 60, the latter otherwise known as a PSTN, acustomer's NAS 63, an IP network 66, a lab NAS 70 and a test workstation74. The user's modem 56 is connected to the PSTN 60 through thecommunication line 58 and the PSTN 60 is coupled to the customer's NAS63 through the line 62, which in one embodiment of the present inventionis a T1/E1 line or any Telco Time Division Multiplexed (TDM) transportline such as an optical-OCx, T3/E3 and the like. The customer's NAS 63is coupled to the IP network 66 through the Ethernet connection 64 andthe IP network 66 communicates with the lab NAS 70 through the Ethernetconnection 68. The lab NAS 70 is connected to the workstation 74 throughthe line 72 and the workstation 74 is coupled to the IP network 66through the line 76.

The information originating at the user's PC 52 is converted from adigital format to an analog format by the user's modem 56 andtransmitted to the PSTN 60. Inside of the PSTN 60, the analog signalsare digitally encoded by a subscriber line interference card (SLIC)located at the “edge” of the PSTN where 60 and 58 meet and thereaftertransmitted to the customer's NAS 63. In this respect, the modem that islocated inside of the customer's NAS 63 recognizes them as modem tones.Thereafter, the voice signals are transmitted over the IP network 66using the two modes of tunneling described hereinabove.

If the modem fails to connect with the NAS 63, the call ends. Then, theNAS 63 has to be configured to treat the next call as a VoIP call andtunnel the voice signals to the NAS 70. The customer's NAS 63 convertsthe voice signals, being in the form of PCM samples, into RTP packetsand transmits the same to the IP network 66, as shown in FIG. 2. In thiscase however, the voice signals are processed through the hardware thatis located within the modem in the customer's NAS 63. This is donewithout the modem software code being executed and the modem, in thecustomer's NAS 63, operates as a straight pipe for passing the voicesignals therethrough, the modem in the customer's NAS 63 having buffersfor handling the latency and delays through the network. The IP network66 subsequently forwards the information packets to the modem that islocated inside of the lab NAS 70 at which point the call is terminatedand the information is analyzed in order to debug the modem problem inreal-time. This is particularly useful because at the lab, the testworkstation 74 having appropriate probes for test purposes is availablethereby rendering troubleshooting/debugging an easier task than to haveto do the same in the field where the problematic modem is located.Furthermore, debugging takes place in real-time resulting in a moreaccurate representation of the nature of the problem that is beingdiagnosed.

Moreover, in the lab as much recording and logging as is necessary canbe performed thereby resulting in greater advantage over dispatchingequipment as is done in the prior art, which has obvious limitations,some of which are enumerated hereinabove.

There are a number of parameters such as a local carrier loop, carrierequipment, and the customer's local loop that can cause a modem to fail.Local carrier loop is the circuit 50, which carries analog signals fromthe modem 56 to the Telco network 60. Malfunctions are prevalent withrespect to this connection due to a lack of a controlled environment.For example, typically, the connection from the modem 56 to the Telconetwork 60 is a telephone cable or an extension in a user's home.Carrier equipment is the circuit switch and the subscriber lineinterface card (SLIC) at the edge of the Telco network 60, whichconnects to the local carrier loop 58. Since the carrier equipmentcarries analog information, it is more susceptible to problems such asnoise. Customers's local loop is the same as the local carrier loop whenit is connected to a local PSTN network, which may be owned privatelyand not under the control of an authority.

When the relevant parameters are identified and debugging is completedat the test station 74, appropriate action can be taken on the customerserver modem in the NAS 63, the modem in the PC 52 or the PSTN 60. Inthis manner, by terminating the call at the lab modem, the equipment inthe lab is placed at the customer's site in a virtual sense for thepurposes of debugging and diagnostics.

FIG. 3 illustrates a flow chart of a voice signal through the customer'sNAS 63. The voice signals, in the form of digitally encoded analogsignals, arrive at the customer's NAS 63 via the transmission line 80.The signal goes through various layers in the NAS 63, as depicted inFIG. 3.

In order to terminate the voice call at the lab NAS 70, as shown in FIG.2, the software residing in the NAS 70 need be modified. The software ina typical NAS includes an internetworking operating system (IOS) and themodem firmware. The IOS is the operating system for the network accessservers in much the same way as Windows 98 is an operating system for aPC.

The modem firmware module 81 as shown in FIG. 3 receives the digitallyencoded analog signals. The modem firmware module 81 consists ofmultiple layers. In layer one, 82, modulation/demodulation of the voicesignals is performed whereby the voice signals are turned into bits andvice-versa. In layer two, 84, of the modem firmware module 81,compression and decompression of the data as well as error correctiontake place. The voice signals are transmitted to the layer three Bridge88, as indicated by the arrow 86 in FIG. 3. At step 88, the data areencapsulated into well-defined IP packets and transmitted to the layerthree routing 92 as indicated by the arrow 90.

At step 92, it is determined through one of the input/output ports theIP packets are routed through to their final destinations. This is donebased upon the IP packets' designated IP address.

The IP packets are now ready to be routed to the IP network 66. For thispurpose, they are transmitted to the layer three routing 96 as indicatedby the arrow 94 where an IP routing engine sends them, via the layernetwork interface 100, otherwise known as Ethernet, to the Internet BackBone 104. The arrow 102 in FIG. 3 indicates the latter transmission.

The customer's NAS 63 (shown in FIG. 2) includes a processor (notshown), or computer medium, some type of storage area and a computerreadable medium, for storing the software/firmware described in FIG. 3.The processor executes code from the computer readable medium foreffectuating the functions outlined in FIG. 3.

Although the present invention has been described in terms of specificembodiments it is anticipated that alterations and modifications thereofwill no doubt become apparent to those skilled in the art. It istherefore intended that the following claims be interpreted as coveringall such alterations and modification as fall within the true spirit andscope of the invention.

What is claimed is:
 1. A network communication system for communicatinginformation between two modem devices using a pass-through mode oftunneling through a packet switching network comprising: a lab networkaccess server coupled to a first modem device, through the packetswitching network, said lab network access server for communicating to acustomer network access server including a customer modem device,through the packet switching network, the customer network access serverbeing coupled to communicate with a second modem device, wherein thesecond modem device establishes a call to the first modem device throughthe customer network access server for communicating information betweenthe first and second modem devices and upon the customer modem devicefailing to successfully communicate with the first modem device, saidlab network access server for receiving a succeeding call from thesecond modem device using a pass-through mode of tunneling, through thepacket switching network, and terminating the succeeding call therebyallowing diagnosis and debugging of the failure associated with thecustomer modem device at the location of the lab network access server.2. A network communications system as recited in claim 1 wherein saidlab network access server includes a lab modem device for terminatingthe succeeding call.
 3. A network communications system as recited inclaim 1 wherein said lab network access server communicates with thefirst modem device through a public switching telephone network.
 4. Anetwork communications system as recited in claim 1 further including adestination network access server coupled between said lab networkaccess server and the first modem device for communicating informationtherebetween and through the public switching telephone network.
 5. Anetwork communications system as recited in claim 1 wherein the call isconverted into packets of voice samples by the customer network accessserver prior to transmission thereof to the lab network access server.6. A network communications system as recited in claim 5 wherein anaddress identifying the destination of the call is transmitted with thepacketized voice samples to the lab network access server.
 7. A networkcommunications system as recited in claim 5 wherein the voice samplesare converted into packets using Real-time Transport Protocol (RTP). 8.A network communications system as recited in claim 7 wherein thecustomer modem device is caused to operate as a straight pipe forpassing the voice samples therethrough without processing the same.
 9. Anetwork communications system as recited in claim 8 wherein the customermodem device includes buffers for compensating for latency and delaysassociated with the packet switching network.
 10. A networkcommunications system as recited in claim 1 wherein the lab networkaccess server for terminating the succeeding call thereby offering amodem wholesale to customers having only voice-over-IP capability at thelocation of the lab network access server.
 11. A lab network accessserver coupled to a customer network access server through a packetswitching network, the customer network access server including a firstmodem device, which is coupled to a second modem device through a publicswitched network, the lab network access server for diagnosing problemsassociated with the first modem device and comprising a lab modem devicewherein the second modem device establishes a call to the first modemdevice through the customer network access server for communicatinginformation between the first and second modem devices and upon thefirst modem device failing to successfully communicate with the secondmodem device, said lab modem device for receiving a succeeding call fromthe second modem device using a pass-through mode of tunneling, throughthe packet switch network, and terminating the succeeding call therebyallowing diagnosis and debugging of the failure associated with thefirst modem device to be performed at the location of the lab networkaccess server.
 12. A lab network access server as recited in claim 11wherein said lab network access server communicates with the first modemdevice through an Internet Protocol (IP) network.
 13. A lab networkaccess server as recited in claim 11 wherein the call is converted intopackets of voice samples by the customer network access server prior totransmission thereof to the lab network access server.
 14. A lab networkaccess server as recited in claim 11 wherein an address identifying thedestination of the call is transmitted with the packetized voice samplesto the lab network access server.
 15. A lab network access server asrecited in claim 11 wherein the voice samples are converted into packetsusing Real-time Transport Protocol (RTP).